1. Field of the Invention
The present invention relates to a method and apparatus for reading image information on a medium, and an image reading and recording apparatus including the image reading apparatus.
2. Description of the Related Art
Image scanners, copiers, facsimiles, multifunction printers, and the like include image reading apparatuses. In such an image reading apparatus, a reading medium, such as a paper document, is illuminated, and the illuminated surface is optically read with a line sensor. To illuminate the reading medium, a light source capable of providing line illumination, such as a cold cathode fluorescent tube or a xenon tube, is commonly used. In place of such a light source, a growing number of recent apparatuses employ other light sources in each of which a plurality of white-light-emitting diodes (white LEDs), serving as point light sources, are arrayed. Direct use of such an illumination unit including a plurality of point light sources often produces nonuniformity in illuminance. To solve this problem, Japanese Patent Laid-Open No. 2005-156600 and No. 2007-158379, for example, disclose techniques for reducing nonuniformity in illuminance by diffusing light from point light sources through light-diffusing members.
In these techniques, however, if the medium to be read is not a paper document but a surface containing a reflective diffraction surface, for example, the label side (the side where the title of content and so forth are printed) of a disc medium such as a compact disc (CD), the reflective diffraction surface causes diffraction, and interference due to the diffraction may cause nonuniformity (nonuniformity in color and brightness) in the read image.